The subject matter herein relates generally to methods and systems of determining a crimp height of a crimped electrical connection.
Terminals are typically crimped onto wires by means of a conventional crimping press having an anvil for supporting the electrical terminal and a ram that is movable toward and away from the anvil for crimping the terminal. In operation, a terminal is placed on the anvil, an end of a wire is inserted into the ferrule or barrel of the terminal, and the ram is caused to move toward the anvil to the limit of the stroke of the press, thereby crimping the terminal onto the wire. The ram is then retracted to its starting point.
In order to obtain a satisfactory crimped connection, the crimp height and other characteristics of the crimped terminal must be closely controlled. The crimp height of a terminal is a measure of height or maximum vertical dimension of a given portion of the terminal after crimping. Ordinarily, if a terminal is not crimped to the correct crimp height for the particular terminal and wire combination, an unsatisfactory crimped connection will result. Some systems measure crimp height by manual measurements of the terminals which can be slow and tedious. Some systems measure crimp height based on ram displacement measurements. For example, simple non-destructive means of detecting such defective crimped connections by accurately measuring crimp height during the crimping process is disclosed in U.S. Pat. Nos. 4,856,186 and 4,916,810 to Yeomans.
On the other hand many unsatisfactorily crimped connections will, nevertheless, exhibit a “correct” crimp height. A crimp height variance or other physical variation in the crimped terminal is not in and of itself the cause of a defective crimp connection, but rather, is indicative of another factor which causes the poor connection. Such factors include using the wrong terminal or wire size, missing strands of wire, wrong wire type, and incorrect stripping of insulation. Since such defective crimped connections frequently have the appearance of high quality crimped connections, it is difficult to identify these defects so that timely corrective action may be taken. Simple non-destructive means of detecting defectively crimped terminals by analyzing the crimping forces imposed on the terminal during the crimping operation are disclosed in U.S. Pat. Nos. 5,123,165 and 5,197,186 to Strong. However, estimates of crimp height and poor quality crimps based on force measurements are unreliable due to unexpected changes in the crimp force and crimping machine component positions. In addition, force based estimates of crimp height require complex computer systems to interpret force and position data to develop the estimated crimp height.
New technologies in ultrasonic monitoring have been proposed for use in crimp quality monitoring. For example, U.S. Pat. No. 7,181,942 describes an ultrasonic device and method for measuring crimp connections by comparing signals with signals from a previous crimp that was determined to be desirable through destructive testing.
A need remains for a crimp quality monitoring system that uses ultrasonic monitoring to determine crimp height of a crimped terminal as a measure of crimp quality.